Toward a compact levitated superconducting dipole for positron-electron plasma confinement

This paper describes the design of a compact levitated superconducting coil for the production of a magnetic dipole field to eventually trap positron-electron plasma. The closed 300 turn coil is to be constructed from Bi-2223 high-T_c superconducting tape, directly cooled on a cryogenic cold head (with thermal contact enhanced using helium gas), and inductively energized with a second superconducting coil mounted on the same cold head. Levitation will be achieved from above using a water-cooled copper coil outside the vacuum chamber and its current will be feedback controlled using vertical position information from a laser ranger.